The changes of morphology and protein pattern of sarcoma 180 cells treated with or without trannins extracted from persimmon leaves were evaluated by light microscopy, electrophoresis and Western blotting. The sarcoma 180 cells treated with tannins increased the amount of proteins which presumably were intermediate filament cytokeratins detected by electrophoresis and Western blot. Tannins was indirectly cytotoxic to the sarcoma 180 cells and increased the intermediate filament protein level in the cells.